1. Field of the Invention
The present invention relates to a filter formed by folding a filter element into zigzagged, corrugated or pleated configurations, and is preferably applied to an air filter having a deodorant function.
2. Description of the Related Art
Conventionally, an air filter for filtering and deodorizing air for an air conditioner has been known, in which a filtering body is made from an air filtering sheet containing deodorant as an air filter element and formed into a zigzagged shape by folding the air filtering sheet along multiple parallel, straight folds (hereinafter referred to as the deodorant air filter).
Accordingly, such a filter body has a shape made up of a series of filter pieces sectionally formed between a pair of adjacent folds in the filter sheet, and a pitch between each of folds, i.e., a length of each piece of the filter sheet, is equally formed.
However, in the above-mentioned conventional deodorant filter, since the shape of the filter body is primarily defined by dimensions in the directions of face and thickness, there has been no way to improve the filter's deodorizing ability other than to increase the number of filter pieces forming the filter body by reducing the pitch between each of the folds.
On the other hand, although ventilation resistance and pressure loss are improved to some extent by reducing the pitch between each of the folds, in case the pitch is beyond the optimal pitch, a clearance between two adjacent pieces becomes too narrow, as a result, the ventilation resistance and pressure loss increase.
Consequently, the conventional filter body has a problem that ventilation resistance and pressure loss increase as the number of pieces of sheet forming the filter body increase by reducing the pitch between the folds in order to improve deodorizing ability.
Instead of increasing the number of filter pieces forming the filter body by reducing the pitch between the folds, it is also possible to improve deodorizing ability by increasing the thickness of the filter sheet, that is, by increasing the amount of deodorant to be adhered. However, such a thick sheet makes ventilation resistance and pressure loss increase and also makes the process of folding the sheet difficult.
Furthermore, an equally-pitched conventional filter has a problem that, when it is installed to cover a wide area in a plane form, it deforms, thereby giving way to air flow (the fluid to be filtered) due to a low bending strength in a direction of the sheet's thickness. Particularly, there has been a problem that air flow quantity may be reduced for filtering ability may be deteriorated when the filter deflects towards the downstream direction, the top portion of the folded filter element deforms into a meandering shape, or pieces of the filter element stick together closely. Such a problem is likely to occur when ventilation resistance increases due to the clogging of a filter element which has been used for a long period of time, or under environments of high temperature and high humidity. Particularly, since a filter for purifying air mounted on an inlet port of an air conditioner for vehicles is used under automotive conditions providing a high temperature environment and a high humidity environment, it is likely that the adhesive strength of hot melt type adhesive used for bonding the filter is deteriorated due to the high temperature, or the rigidity of filter element made of paper is deteriorated due to high humidity and rain water penetration. For these reasons, improvement of the filter has been greatly needed.